Is the position of a star as seen by us its true position? Justify your answer.

Explain why stars twinkle while planets do not.

Which of the following two colors are complementary colors?

$A$ $14$ year old student is not able to see clearly the questions written on the blackboard placed at a distance of $5\, m$ from him.
$(a)$ Name the defect of vision he is suffering from.
$(b)$ With the help of labelled ray diagrams show how this defect can be corrected.
$(c)$ Name the type of lens used to correct this defect.

$A$ child sitting in a classroom is not able to read clearly the writing on the blackboard.
$(a)$ Name the type of defect from which his eye is suffering.
$(b)$ With the help of a ray diagram show how this defect can be remedied.

Which colour has the maximum wavelength and which has the minimum wavelength? Explain on the basis of wavelength which colour bends the most and which colour bends the least.